Revert "sha2: undef BYTE_ORDER before using"

This reverts commit e01f3a6eacdc9999d75da7b2cb1f1c2b6c64b66c.

BYTE_ORDER should be set by the Makefile depending on the target this
is build for. A following commit will set this define in the makefile
for two new targets.

Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>
dtls: add support for wismote and exp5438

The endianes has to be defined for wismote and exp5438.

Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>
debug: Do not use snprintf() with a vaiable length

The compiler for the MSP430 on contiki thinks that the length is not a
build in constant and makes this function fail every time. The length
is already checked before, so it is save to use sprintf() instead.

Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>
debug: do not add va_list to pirntf function

When the target does not support vprintf() (HAVE_VPRINTF is not set) do
not add the arguments normally added to vprintf to printf, but replace
our nice debug function  dsrv_log() with a call to printf().

Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>